Offshore platforms are used for processing well fluid from subsea wells. Early offshore structures were supported from the bottom or sea floor. Sea floor supported platforms are still often used in shallow water. When the wells are depleted, most governments require that the structure be removed. These bottom supported platforms, being embedded in the sea floor, are not reused, rather are scrapped at considerable expense after one use. The removal costs are particularly high because these platforms are normally too large to be lifted out of the water, therefore must be cut up and dumped in approved offshore deep water dumping sites.
Floating offshore platforms are utilized in deeper water. These floating structures include tension leg platforms and spars, both of which are moored to the sea floor by tension legs or catenary lines. Because deep water floating platforms are very costly, their use has been restricted to only large field developments.